INDUCTION OF EXPRESSION OF MDR 1 GENE BY RETINOIC ACID AND DMSO AND EFFECTS ON RHODAMINE-123 EFFLUX IN HL-60 CELL LINES AND RESISTANT SUBLINES

Using dot blot hybridization and flowcytometry, the effects of differentiation inducers retinoic acid (RA) and dimethyl sulfoxide (DMSO) on the resistant level of HL-60 cells cells and its resistant subline cells were studied. When the cells were treated with RA 1μmol·ml^-1 for 24h, the expression of MDR 1 mRNA evidently increased in both HL-60 and its multidrug resistant subline cells. The efflux of Rho-123 in the multidrug resistant subline cells was slightly decreased. But, when the cells were treated with 2% DMSO for 24h the efflux of Rho-123 increased obviously. The results suggest that RA can induce the expression of MDR1 gene but perhaps inhibit the function of pump glycoprotein 170(Pgp-170) through phosphorylation/dephosphorylation pathway. However, DMSO could induce the expression of full function of Pgp.